Free Software IF

Free Software IF is interactive fiction that is released under a license that gives the user:

the freedom to run the program for any purpose;

the freedom to study and modify the program;

the freedom to copy the program;

the freedom to improve the program, and release your improvements to the public.

Since modifying a program requires access to its source code, free software is automatically also open source software. The reverse is not automatically true: if an author were to release the source code to his game under a Creative Commons Attribution-Non-Commercial-No Derivative Works 3.0 license, for instance, the game would be open source but not free (since distribution of derivative works is not permitted). As another example, the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported license is also not a free software license, since it does not allow people to use the code in certain works, namely commercial ones.

Free software is distinct from freeware, which is software made available free of charge but which usually can't be modified by the users. The word free in "free software" means free as in freedom, but in "freeware", it means free of charge.

Interactive Fiction released under a Free Software License

GNU General Public License

The most used free software license if the GPL, which is maintained by the Free Software Foundation. The GPL is a copyleft license, which means that all derative works have to be licensed under the GPL as well. This ensures that all derative works are also free software.

GPL version 2

The GPL version 2 was released in 1991. Interactive Fiction released under this license includes:

GPL version 3

The GPL version 3 was released in 2007 to address the issues of software patents, hardware restrictions on software modification ("tivoization"), compatibility with other free software licenses, and internationalization. Interactive Fiction released under this license includes:

Fate by Victor Gijsbers, Inform 7 (the competition release reads 'version 2 or any later version').

Iraqi Invasion by Anonymous, Inform 7. (With 'or any later version' designation. It is uncertain whether the author actually can release this work under the GPL, since it incorporates text copyrighted by Matthew Baldwin. This text is used "by permission", but the extent of the permission is not made clear, and the author "strongly recommends you seek additional permission from Mr. Baldwin before making changes that would cause any deviation from the standard transcript".)

BSD Licences

BSD licenses represent a family of permissive free software licences.
The licenses have few restrictions compared to other free software licenses such as the GNU General Public License or even the default restrictions provided by copyright, putting it relatively closer to the public domain.

Night at the Computer Center by Bonni Mierzejewska, Inform 6. ("All rights freely given away, except you may not distribute a modified night.z5 as if it were from me. Ya gotta put yer own name on it, and ya gotta give credit where it's due.")

Public Domain

Some works are designated 'public domain'. On a plausible interpretation, this means that the author has relinquished all copyright over the work, automatically making the work free software if the source code has been made available.

MIT License

The MIT License is a very short, straightforwardcopyleft free software license. It is GPL-compatible, which means that projects released under the MIT-license can be combined with projects released under the GPL-license. (Since both licenses are copyleft, the resulting work would have to be distributed under the conjunction of the MIT license and the GPL.)